My mesh is pink in weight painting
The weight paint pink color tells you that you are trying to assign weight relatively to a bone which has no vertex group assopciated, because it's a non-deforming bone: all rigify rig works in a way in which the controllers bones are different than the deforming bones.



If you want to assign weight controlled by the "head" bone you will have to check the "deforming" option and create a vertex group with the same exact name.